Pneumatic drill for boring

ABSTRACT

The invention is concerned with a pneumatic drill for use in a borehole having a tubular body enclosing a shock-absorbing piston through which the compressed air is supplied, a distributor unit, a percussion piston, and a drill bit which receives the blows from the percussion piston and transmits them to the rock. The percussion piston is movable in a cylinder formed by an inner liner, and between the liner and the inside wall of the drill body lie longitudinal passages for the supply of compressed air to operate the piston and other passages for the discharge of the air after it has acted on one of the faces of the percussion piston. The invention provides in such a drill a flushing fluid supply means which bypass the percussion piston and drill bit by way of longitudinal ducts for the fluid extending from a distributor to escape ducts extending through the body.

United States Patent Stenuick [54] PNEUMATIC DRILL FOR BORING [72] Inventor: Marcel Stenuiek, Fontaine LEveque,

Belgium 7 [73] Assignee: S.P.R.L. Stenuick Freres, Hainaut, Belgi- [22] Filed: Feb. 16, 1970 [21 Appl. No.: 11,588

[ Feb. 8, 1972 2,942,578 6/1960 Huffmanetal .1 ..173/78 3,198,264 8/1965 Oelkeetal ..l73/78 Primary Examiner.lames A. Leppink Attorney-Cameron, Kerkam & Sutton ABSTRACT The invention is concerned with a pneumatic drill for use in a borehole having a tubular body enclosing a shock-absorbing piston through which the compressed air is supplied, a distributor unit, a percussion piston, and a drill bit which receives the blows from the percussion piston and transmits them to the rock. The percussion piston is movable in a cylinder formed by an inner liner, and between the liner and the inside wall of the drill body lie longitudinal passages for the supply of compressed air to operate the piston and other passages for the discharge of the air after it has acted on one of the faces of the percussion piston. The invention provides in such a drill a flushing fluid supply means which bypass the percussion piston and drill bit by way of longitudinal ducts for the fluid extending from a distributor to escape ducts extending through the body.

3 Claims, 2 Drawing Figures PNEUMATIC DRILL FOR BORING The invention relates to a pneumatic drill for boring, having means for simultaneously supplying flushing fluid in order to facilitate the work of the drilling tool by removing the rock debris or cuttings as the drill produces them.

It relates more particularly, by way of example, to a pneumatic drill adapted to operate directly on the bottom of the borehole and coupled to a series of borehole tubes which transmit to it the compressed operating air and the general rotary motion within the borehole. When a drill is used in this way, it is essential to remove the cuttings as they arise, generally by means of fluid which is injected under pressure into the bottom of the borehole and carries the cuttings with it as it returns to the surface.

Pneumatic drills exist which enable pressurized liquid or gaseous fluid to be supplied to the bottom of the borehole completely independently of the supply of compressed operatmg arr.

A pneumatic drill for use at the bottom of a borehole is known having a tubular body enclosing a shock-absorbing piston through which the compressed air is supplied, a distributor unit, a percussion piston, and a drill bit which receives the blows from the percussion piston and transmits them to the rock. The percussion piston is movable in a cylinder formed by an inner liner, and between the liner and the inside wall of the drill body lie longitudinal passages for the supply of compressed air to operate the piston and other passages for the discharge of the air after it has acted on one of the faces of the percussion piston. Such a drill is hereinafter referred to as of the type described.

When drills of the type described are designed for a separate supply of flushing fluid, an axial connecting member is provided for connection to the tube which brings fluid along the borehole tubing, and an axial tube which extends through the entire drill assembly (shock-absorbing piston, distributor unit and percussion piston), ending in an axial bore in the bit.

This arrangement has the serious disadvantage of weakening, with a central hole, the two components subject to the greatest stresses during operation of the drill, that isto say, the percussion piston and the bit itself. As a result, these components have a much shorter service life and must be changed much more often. In the case of deep drilling, of course, the operation of changing the bit is expensive, since the drill must be raised to the surface. Whenever the nature of the terrain makes it possible to operate without flushing fluid, therefore, drills are used which have no flushing-fluid tube and can use solid pistons and bits, so that the number of raising operations is reduced. It is then necessary, however, to keep two stocks of bits and percussion pistons, one with and one without holes for the passage of the tube, and to use two types of drill, depending on the nature of the terrain.

Also, since the piston and bit must not be weakened excessively, the flushing-fluid supply tube must have a narrow diameter, so that the rate of flow of this fluid is very restricted.

It is an object of the invention to provide an improved pneumatic drill for use with flushing fluid.

According to the invention there is provided a pneumatic drill for boring, permitting the drilling zone to be supplied continuously with a flushing fluid which is independent of the compressed operating air and adapted to promote discharge of the cuttings, having a tubular body, a connecting member which can be connected to borehole tubing and has means for connection to a compressed-air source and to an axial flushing-fluid inlet, a shock-absorbing piston attached to the connecting member and containing an axial bore for passage of the compressed air, a distributor unit, an inner lining forming a cylindrical chamber communicating through intake and escape ports with separate, peripheral, longitudinal passages formed between the liner and the inside surface of the tubular body, a percussion piston slidable in the cylindrical chamber inside the liner and operable by the compressed air, means for feeding the compressed air alternately to each of the faces of the percussion piston, a drill bit which is struck by the percussion piston, and escape ducts for the compressed operating air leading to that end of the drill which bears the bit, characterized in that an axial duct connects the connection means for the flushing-fluid supply to a distributor member situated along the axis of the distributor unit, and independent, peripheral, longitudinal passages formed between the liner and the inside surface of the tubular body, these passages communicating at the top with the distributor member through radial ports formed in the distributor unit, and at the bottom with escape ducts leading to that end of the drill which bears the drill bit.

The invention will be clearer from the more detailed description, given by way of example, comparing a conventional drill with a drill embodying the invention. Both drills are illustrated in the accompanying drawings in which:

FIG. 1 shows a longitudinal section through a conventional drill of the prior art permitting continuous use of flushing fluid during boring. The two portions shown side by side are connected to one another and form the upper and lower portions of the same drill, and

FIG. 2 is a similar view, with an additional partial section, of a drill embodying the present invention.

As FIG. 1 shows, the conventional pneumatic drill of the prior art for use with flushing fluid has a tubular body 1, to the upper portion of which a shock-absorber casing 2 and a shockabsorber sleeve 3 are fitted. A shock-absorbing piston 4 movable in the casing 2 and sleeve 3 is guided by ribs 5 engaging corresponding grooves in the sleeve 3. The upper portion of the piston 4 is screwed into an intermediate member 6, to which the borehole tubing can be fixed. The lower portion of the body 1 receives a tool-supporting chuck 7 engaged by a bit 8, which is held by a cotter pin 9.

The shock-absorber casing 2 and chuck 7 hold a distributor unit 10, containing valves, a liner 11 and a sleeve 12 in position between them, inside the body 1. A percussion piston 14 moves freely in the chamber 13 inside the liner 1] and has an extension 15, which engages in the sleeve 12 and, when lowered, comes into contact with the bit 8.

The liner 11 contains a first series of longitudinal intake grooves 20, whose top ends give on to the distributor unit and which are closed at the bottom and communicate with the chamber 13 through intake ports 21. The liner 11 also contains a second series of escape grooves 22, which are closed at the top and lead at the bottom to grooves 23 formed in the sleeve 12. These escape grooves 22 communicate with the chamber 13 through escape ports 24.

In the operating position, as shown in the drawing, pressure is exerted by the borehole tubing on the intermediate member 6, and the end 16 of the shock-absorbing piston 4 enters a bore 17 in the distributor unit 10. The compressed air entering the intermediate member at 25 then flows into ducts 26, along a bore 27 inside the shock-absorbing piston 4, out of this bore through ports 28, and in through ports 29 into the distributor unit 110. Due to the action of the valves in the distributor unit, the compressed air flows alternately to the upper surface of the piston 14, through ports 30, or to the lower surface of the piston 14, through ports 31, the grooves 20 and the ports 2]. In either case, after moving the piston 14, it escapes through the ports 24, grooves 22 and grooves 23. It then expands in a chamber 32 in the chuck 7, and escapes from the drill along ducts 33.

If the pressure on the drill is removed, the end lb of the piston 4 withdraws from the bore 17, and the effect of the distributor unit is cancelled out, the compressed air flowing simultaneously to the upper surface of the piston 14 through the bore 17 and to its lower surface through the ports 31, grooves 20 and ports 21.

The pressurized water used as the flushing fluid is fed to the borehole tubing through an axial tube fitted to a connection 35 on the intermediate member 26. An axial tube 36 fixed to this connection extends through the bore 27 in the shock-absorbing piston 4, out of the end 16 of this piston, along the bore 17 in the distributor unit 10, through the whole of the percussion piston 14, and into a bore 37 situated along the axis of the bit 8. Radial ducts 38 leading into this axial bore 37 carry the flushing water to the periphery of the bit.

In FIG. 2 illustrating the present invention, like elements which are functionally equivalent to those in the drill shown in FIG. I bear like reference numerals, and the drilling mechanism proper operates as described above. In FIG. 2, however, the section through the liner 11, showing the intake grooves 20 and their connection to the distributor unit and chamber 13, has been transferred to the additional partial section represented beside the main Figures.

In the drill shown in FIG. 2, the distributor unit 10 has a distributor member 40, fixed to the end of an axial tube 41. Ports 42 in the distributor member open on to an annular inner chamber 43, communicating through ducts 44 with a second, outer annular chamber 45. As in the drill shown in FIG. 1, the tube 36 extends into the axial bore in portion 16 of the piston 4, but the tube 36 ends in this bore. The other end of this bore receives the tube 41. Rings 46 at both ends ensure fluidtightness.

The liner 11 contains a third series of longitudinal grooves 47, whose top ends communicate with the chamber 45 through ports 48. These grooves 47, which are closed at their lower ends, communicate through ports 49 with an annular chamber 50 in the sleeve 12. This chamber 50 in turn communicates, by way of ducts 51, with the escape grooves for the operating air.

The tube 41 penetrates sufficiently far into the portion 16 to remain engaged in it even when the shock-absorbing piston 4 is in its limit position.

The pressurized water supplied to the connection 35 passes through the drill, flowing along the tube 36, the bore inside the portion 16, the tube 41, the ports 42, the chamber 43, the ducts 44, the chamber 45, the ports 48, the grooves 47, the ports 49, the chamber 50 and the ducts 51. The water then mixes with the air expanding in the grooves 23 and chamber 32, and is sprayed around the bit through the ducts 33.

In a drill of this kind, embodying the invention, the percussion piston and bit are exactly the same as those used in a drill of the same caliber without any flushing-fluid supply, and their strength and behavior during operation are, of course, equivalent.

The tube 36 supplying pressurized water can easily be made larger in diameter than those in earlier drills, since it does not extend through any highly stressed component. On the contrary, it extends only through the portion 16 of the shock-absorbing piston, which merely forms a slide valve for operating the distribution mechanism. A larger-diameter supply tube can, of course, supply flushing water to the bottom of the borehole at a faster rate, so facilitating removal of the cuttings.

Also, the mixing of the water with the expanding air produces a spray and reinforces the flushing action of the pressurized water.

Obviously, the invention does not relate only to the embodiment described by way of example, but also to others which differ from it only in detail. For example, depending on the nature of the fluid, it may be preferable not to mix it with the expanding air, and the escape ducts for the air and fluid might be separate. Also, the flushing fluid might simply be compressed arr.

I claim:

1. A pneumatic drill for boring, continuously supplying the drilling zone with a flushing fluid independent of the compressed operating air for discharge of the cuttings, comprising a tubular body, a connecting member connected to borehole tubing, means for connection of said body to a compressed air source and to an axial flushing-fluid inlet, a shock-absorbing piston attached to said connecting member, an axial bore in said piston for passage of the compressed air, a distributor unit, an inner lining in said body forming a cylindrical chamber, intake and escape ports through said liner communicating with separate, peripheral, longitudinal passages between said liner and the inside surface of said tubular body a double percussion piston slidably mounted in said cylindrica chamber operable by the compressed air, means for feeding the compressed air alternately to each of the faces of said percussion piston, a drill bit struck by said percussion piston, escape ducts for the compressed operating air leading to the bit end of said drill, an axial duct between said connection means for the flushing fluid and said distributor unit on the axis of said distributor unit, and independent, peripheral, longitudinal passages between said liner and the inside surface of said tubular body, said last-named passages communicating at the top with said distributor unit through radial ports in said distributor unit, and at the bottom with escape ducts leading to that end of the bit end of said drill.

2. A drill as claimed in claim 1, said axial duct between said connection means for the flushing-fluid inlet and said distributor unit including a first axial tube connected to the inlet connection and attached to said shock-absorbing piston, a second fixed axial tube connected to said distributor unit, and a tubular axial sleeve attached to said shock-absorbing piston and connecting the free ends of each of said two tubes, said second axial tube engaging said sleeve by a sealing member engaged therein at all positions of said shock-absorbing piston.

3. A drill as claimed in claim 2, said longitudinal, peripheral passages for the flushing fluid leading into the same escape ducts as those for the compressed operating air. 

1. A pneumatic drill for boring, continuously supplying the drilling zone with a flushing fluid independent of the compressed operating air for discharge of the cuttings, comprising a tubular body, a connecting member connected to borehole tubing, means for connection of said body to a compressed air source and to an axial flushing-fluid inlet, a shock-absorbing piston attached to said connecting member, an axial bore in said piston for passage of the compressed air, a distributor unit, an inner lining in said body forming a cylindrical chamber, intake and escape ports through said liner communicating with separate, peripheral, longitudinal passages between said liner and the inside surface of said tubular body, a double percussion piston slidably mounted in said cylindrical chamber operable by the compressed air, means for feeding the compressed air alternately to each of the faces of said percussion piston, a drill bit struck by said percussion piston, escape ducts for the compressed operating air leading to the bit end of said drill, an axial duct between said connection means for the flushing fluid and said distributor unit on the axis of said distributor unit, and independent, peripheral, longitudinal passages between said liner and the inside surface of said tubular body, said last-named passages communicating at the top with said distributor unit through radial ports in said distributor unit, and at the bottom with escape ducts leading to that end of the bit end of said drill.
 2. A drill as claimed in claim 1, said axial duct between said connection means for the flushing-fluid inlet and said distributor unit including a first axial tube connected to the inlet connection and attached to said shock-absorbing piston, a second fixed axial tube connected to said distributor unit, and a tubular axial sleeve attached to said shock-absorbing piston and connecting the free ends of each of said two tubes, said second axial tube engaging said sleeve by a sealing member engaged therein at all positions of said shock-absorbing piston.
 3. A drill as claimed in claim 2, said longitudinal, peripheral passages for the flushing fluid leading into the same escape ducts as those for the compressed operating air. 